On Fri, Mar 7, 2025 at 1:45 AM Alistair Francis <alistai...@gmail.com> wrote:
> I'm not convinced that this is the thing that we should be checking
> for. If someone can corrupt the migration data for an attack there are
> better things to change then the MXL
In principle you could have code that uses 2 << MXL to compute the
size of a memcpy, or something like that... never say never. :)
Do you prefer turning all the priv_ver, vext_ver, misa_mxl,
misa_ext_mask fields into VMSTATE_UNUSED? That would also be okay.
I would also add a check for misa_ext against misa_ext_mask and
riscv_cpu_validate_set_extensions().
Paolo
> Alistair
>
> >
> > Paolo
> >
> > > Alistair
> > >
> > >> would have a snowball effect on, for example, the valid VM modes.
> > >>
> > >> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> > >> ---
> > >> target/riscv/machine.c | 13 +++++++++++++
> > >> 1 file changed, 13 insertions(+)
> > >>
> > >> diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> > >> index d8445244ab2..c3d8e7c4005 100644
> > >> --- a/target/riscv/machine.c
> > >> +++ b/target/riscv/machine.c
> > >> @@ -375,6 +375,18 @@ static const VMStateDescription vmstate_ssp = {
> > >> }
> > >> };
> > >>
> > >> +static bool riscv_validate_misa_mxl(void *opaque, int version_id)
> > >> +{
> > >> + RISCVCPU *cpu = RISCV_CPU(opaque);
> > >> + CPURISCVState *env = &cpu->env;
> > >> + RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(cpu);
> > >> + uint32_t misa_mxl_saved = env->misa_mxl;
> > >> +
> > >> + /* Preserve misa_mxl even if the migration stream corrupted it */
> > >> + env->misa_mxl = mcc->misa_mxl_max;
> > >> + return misa_mxl_saved == mcc->misa_mxl_max;
> > >> +}
> > >> +
> > >> const VMStateDescription vmstate_riscv_cpu = {
> > >> .name = "cpu",
> > >> .version_id = 10,
> > >> @@ -394,6 +406,7 @@ const VMStateDescription vmstate_riscv_cpu = {
> > >> VMSTATE_UINTTL(env.priv_ver, RISCVCPU),
> > >> VMSTATE_UINTTL(env.vext_ver, RISCVCPU),
> > >> VMSTATE_UINT32(env.misa_mxl, RISCVCPU),
> > >> + VMSTATE_VALIDATE("MXL must match", riscv_validate_misa_mxl),
> > >> VMSTATE_UINT32(env.misa_ext, RISCVCPU),
> > >> VMSTATE_UNUSED(4),
> > >> VMSTATE_UINT32(env.misa_ext_mask, RISCVCPU),
> > >> --
> > >> 2.48.1
> > >>
> > >>
> > >
> > >
> >
>
